Question: Solve for $x$ and $y$ using substitution. ${-2x-4y = 0}$ ${x = 6y+8}$
Answer: Since $x$ has already been solved for, substitute $6y+8$ for $x$ in the first equation. ${-2}{(6y+8)}{- 4y = 0}$ Simplify and solve for $y$ $-12y-16 - 4y = 0$ $-16y-16 = 0$ $-16y-16{+16} = 0{+16}$ $-16y = 16$ $\dfrac{-16y}{{-16}} = \dfrac{16}{{-16}}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = 6y+8}\thinspace$ to find $x$ ${x = 6}{(-1)}{ + 8}$ $x = -6 + 8$ ${x = 2}$ You can also plug ${y = -1}$ into $\thinspace {-2x-4y = 0}\thinspace$ and get the same answer for $x$ : ${-2x - 4}{(-1)}{= 0}$ ${x = 2}$